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Among the palaemonid shrimp species of the genus Palaemon known from Japan, Palaemon paucidens is the only species inhabiting freshwater areas. Two genetically distinct types (designated by A and B) were found by

Fishery sustainability and the extinction risk of the Japanese eel, Anguilla japonica, are of global concern. The landings of the Japanese eel in Japan comprise a large part of the landings in East Asia. This study provides a compiled dataset of the annual fisheries statistics of the Japanese eel in Japan for stock assessment. The Japanese government has been recording Japanese eel statistics annually since 1984 in five series of annual reports by conducting systematic questionnaire surveys of fisheries managers and associations; however, most of these data are stored in analog format. The key variables in the dataset include the harvest weight of eels, the harvest weight and number of seeds for aquaculture, the number of eels stocked, and the number of management entities engaged in the eel fishery. The levels of spatial aggregation of the variables include the site (river and lake), prefecture, inland and coastal waters, and total in Japan. We also incorporated location data (latitude and longitude) of the site and prefecture into the dataset. Eel harvest includes primarily yellow eels (late juvenile stage) and silver eels (mature stage). Seed harvest in inland waters includes glass eels (intermediate stage between leptocephalus and elver) and elvers (early juvenile stage). Seed harvest from coastal waters comprises glass eels. This dataset provides information to assess long-term trends in the Japanese eel population.

1. Assessing the status or population size of species is a key task for wildlife conservation and the sustainable management of harvested species. In particular, assessing historical changes in population size provides an evolutionary perspective on current population dynamics.2. Japanese eel (Anguilla japonica) is an endangered yet commercially important catadromous fish species. This article assesses the demographic history of Japanese eel using the pairwise and multiple sequentially Markovian coalescent methods.3. The analyses indicate a reduction in effective population size N e from 38,000 to 10,000 individuals between 4 and 1 Mya, followed by an increase to 80,000 individuals between 1 Mya and 22-30 kya. Approximately 22-30 kya there is evidence for a reduction in N e to approximately 60,000 individuals. These events may be related to changes in environmental conditions, especially around the last glacial maximum (19-33 kya).4. The results of this study suggest that Japanese eel has experienced at least two population bottlenecks, interspersed by a period of population growth. The overall level of genetic diversity is relatively low, although there is no evidence for inbreeding. Data from this study will be used to help model the extinction risk of Japanese eel.

Costly anti-predator traits tend to be expressed only in high-predation conditions. For the cyprinid fish genus Carassius, deeper body depth is more adaptive to avoid predation by gape-limited piscivorous fish, but it raises swimming costs. It is therefore predicted that the relative body depth will decrease when the prey fish has reached a size larger than the predator gape-size. This prediction was tested by allometric analysis of the relation between body depth and standard length of triploid asexual females of the Japanese crucian carp (Carassius auratus sspp.) sampled from 13 geographic populations. The overall allometric relation was not significantly different from isometry. The estimate of the common major-axis slope was close to 1 (near-isometry). The mean relative body depth differed significantly among populations. A significant positive correlation was found with the mean annual air temperature. The geographic variation suggests that local selection pressures vary. In conclusion, the hypothesis that larger fish will have lower body depth was not supported, perhaps indicating that deep body depth in large fish is adaptive for some reason other than defense against piscivorous fish.